1. Field of the Invention
This invention pertains to a method and device for controlling a self-propelled floor cleaning vehicle for cleaning the floors of buildings, etc.
2. Related Background Art
Usually, a self-propelled cleaning vehicle is guided by means of a reflective tape bonded onto the floor to be cleaned as described in Japanese Published Patent Application No. 57-128119 to Isamu. However, the reflective tape detracts from the appearance of the floor. Also, as the reflective tape is worn or peeled, the cleaning vehicle cannot be guided correctly. Consequently, the tape has to be changed frequently. This is a disadvantage.
In order to solve the aforementioned problem, the present inventor proposed a new method for guiding a floor cleaning vehicle without using the reflective tape in Japanese Published Patent Application No. 06-149350 published on May 27, 1994 which corresponds to U.S. Pat. No. 5,622,236, entitled "Guidance System for Self Advancing Vehicle" in the names of Yasuhiro Azumi and Mitsuo Sado, the latter of which is hereby incorporated by reference.
In the Azumi and Sado guidance system, a material containing a light-emitting dye is applied on the floor to form a guidance line, on which multiple layers of floor wax or other finishing agent is coated overall on the floor, and the cleaning vehicle is guided along the guidance line.
This method can be used to solve the aforementioned problem.
However, just as in the aforementioned conventional method using reflective tape, since the amount of dirt on the floor is not uniform, dirt may cover portions of the floor coated with the finishing agent, and the gloss of the floor surface may be lost in some areas due to multiple scratches on the finishing agent on the floor surface. Consequently, the dirt may not be cleaned off at a high level of efficiency if the cleaning vehicle runs at a constant speed. In this case, the aforementioned problem is still not solved.
Japanese Published Patent Application No. Hei 2[1990]-56610 to Toshihiro et al. teaches an optical guidance system for moving vehicles. A guide path is coated with a strip of transparent paint that selectively absorbs or reflects light outside of the visible range. A series of three sensors detects light absorbed or reflected from the paint to keep the moving vehicle following the paint line. The center sensor detects the paint strip. The other two sensors monitor the unpainted floor and detect when the vehicle is moving off the paint strip. They steer the vehicle back to following the paint strip. One problem with this system is that dirt on the floor makes it harder for the sensors to keep the vehicle following the paint strip because the dirt makes the paint strip harder to distinguish from the floor next to the strip.